Move system Toast layer to same as system error.

Move the system Toast layer to be the same as the system error. Toasts
are showing below bubbled activities because they are on a lower layer.

Flag: com.android.server.policy.bug_toasts_on_top_of_bubble
Bug: 409222337
Test: manual - use bubbles test app and launch a Toast message.
Change-Id: I0a9c3d3c4db196c9f889c1d86c892755ea5e0559